Ha, fascinating and fun. Also great that you and your daughter had some shed time.

I had a look and followed the link down the page to hear the one you are making, and, as usual got distracted by the other variations on the theme. Some, as is usual on youtube were rubbish others good.

This one from plumbing bits is WAY loud but just shows what can be done acoustically and fun to see. Skip toward the end if you just want to see what he finished up with.

Quite the apparatus he devised - I think it was a joke - at least the writing under the video indicated that.

Anyway we got the project done. A little background. The front part of my shop is under the deck at the rear of our house and two weeks ago I had the decking replaced (5/8 ply) as it was old and starting to delaminate. In the process as I was moving some things on the uncovered deck I fell through a gap and did a number on my left leg. I've been limping around like a one legged pirate since.

Due to the deck repairs, the front part of the shop now has insulation hanging down from the ceiling - I was planning to put it up properly but that hasn't happened as I don't really feel like climbing around on ladders at the moment. My shop is so cluttered I have to take things outside (in the snow and about 0 C weather) if I want to use my planer and table saw. So as you can imaging it was a real comedy of errors making this "amplifier".

We did get it done:

You will likely notice the small cross piece anchored by two brass pins - that was to cover up a mistake. I find in (my) woodworking that being able to make mistakes look like features is very valuable.

The spacers (all along the edge) in this design are about 5/8 in. square section and the front and back pieces are 1/2 in. thick. It seems to me that using spacers that were very thin (eg. 3/16 in wide x 5/8 in thick) and using a thin front and back might make this design resonate and work better. I'm no acoustic engineer so this is just a guess. My changes would make it more like a stringed instrument box. I suspect that making the box bigger would also help.

The box does work moderately well. It gives the phone a deeper sound and does amplify it a bit so in that regards it was a success.

OOPS, just shows that I didn't read the description below the video. You are correct that he did put ("joke") at the end of his description. Silly me.

Your project looks good and the cross piece is not to cover up your mistake, It's a feature. I trust your daughter was pleased with the result.

In our playpens the ability to reclaim stuff that we have made mistakes on is part of the skill set we develop. Crikey, if it were not for that slowly developing skill not a lot would get finished in my shed. I do tend to be ultra careful measure twice, cut once - oops measured twice and still messed up the cut, sort of thing.

I wonder if the sound channel was cut with an expanding width whether there might be more amplification. After all, that's how trumpets work I think.John B

Logged

Converting good metal into swarf sometimes ending up with something useful. ;-)

If you are looking at improving amplification and frequency response, you can do no better than go through Martin.J.King's website http://www.quarter-wave.com/.I can't understand any of the math but if you can, you could create very clever custom designs with the emphasis on performance.